Ethernet is today by far the dominating local-area network (LAN) technology in the World. The term Ethernet refers to the family of network products covered by the IEEE 802.3 standard that defines what is commonly known as the CSMA/CD protocol (Carrier Sense Multiple Access Collision Detect protocol). Ethernet has many attractive features that have made it popular on the market:    it is easy to understand, implement, manage, and maintain,    it allows for low-cost network implementations,    it provides extensive topological flexibility for network installation, and    it guarantees successful interconnection and operation of standards-compliant products, regardless of manufacturer.
Of the listed features the relatively low cost of Ethernet network implementations is perhaps the primary reason for the popularity of Ethernet and since Ethernet is so dominating, components are mass-produced which further contributes to keeping costs down.
The Ethernet technology is increasingly being perceived as a candidate for future carrier-class metropolitan area networks (MAN) and wide-area networks (WAN). However, since the Ethernet technology is connectionless, it does not offer the traffic engineering, routing, protection, and quality of service (QoS) control that are supported by a connection-oriented technology such as Multi-Protocol Label Switching (MPLS).
A connectionless transport mode focuses on the destination address, or other identification, of data packets to be transported on a network, rather than any particular path between source and destination network elements. Ethernet's CSMA/CD protocol, the Internet protocol (IP), IPx and SNA are examples of protocols that use a connectionless mode of transportation. In connection-oriented mode signals are communicated over specified paths from a source network element to a destination network element. Examples of transport technologies that use connection-oriented transport are MPLS, Asynchronous Transfer Mode (ATM), Frame Relay, and packet-over-SONET.
A connection oriented network provides efficient bandwidth management, which enables traffic engineering and QoS control and thus allows for an operator to offer QoS aware services. Advantages of connectionless networks over connection-oriented networks are their simplicity, reliability and scaleability. Thus the connection-oriented and connectionless transport modes have different advantages and are thus differently suitable in different situations and for different types of services. However, since many network operators wish to offer their customers a wide variety of services or may wish to be flexible in terms of their types of offered services, there is a demand for the ability to use both modes of transport in the same network.
A number of solutions that combine connection-oriented and connectionless transport in the same network are known.
U.S. Pat. Nos. 6,151,324 and 6,449,279 describe a method and apparatus for providing connection-oriented switching in a communications network in order to achieve connection aggregation to reduce the total number of connections required between switches. This involves modifying connectionless packets so that they can be sent over a pre-established path between an ingress switch and an egress switch.
The international patent application WO 01/87000 describes a system and method for communicating connectionless and connection-oriented signals using common network elements. A signaling type of each signal is determined and a transport label that indicates the signal's signaling type is appended to each signal. The signals are then transported according to signaling procedures associated with each signal's signaling type.
The IETF draft “Generalized Multi-Protocol Label Switching (GMPLS) Architecture” of August 2002 presents a combination of connectionless and connection-oriented transport in a common network by outlining a standard for Ethernet over MPLS. This standard is based on the encapsulation of Ethernet frames in MPLS frames.
A common drawback of the prior art solutions discussed above is that the cost of implementing them are expected to be relatively high since they either require considerable modifications of standard network nodes or the use of legacy switching nodes that are specifically adapted for connection-oriented transport. Switching nodes for connection-oriented transport are relatively expensive compared to e.g. mass-produced Ethernet network nodes. According to the solutions presented in U.S. Pat. Nos. 6,151,324 and 6,449,279 and WO 01/87000 data packets to be transported are modified which implies that new modified network elements are required in order to implement these solutions. The encapsulation of Ethernet frames in MPLS frames as described in the above-mentioned IETF draft “Generalized Multi-Protocol Label Switching (GMPLS) Architecture” requires the use of relatively expensive legacy MPLS switching nodes.